The use of capacitive techniques provides a convenient and straightforward method of obtaining information from a security document. In particular, information may be obtained from a security document concerning the nature of the document which may include some measure of its authenticity.
The past few years have seen a rapid development in manufacturing security documents which are capable of interacting by capacitive coupling with touchscreens. Touchscreens are common in (but not limited to) smartphones, mobile phones, displays, tablet-PCs, tablet notebooks, graphic tablets, television devices, input devices, PDAs, and/or MP3 devices. These devices are optimised to detect a user's finger or a stylus that is brought into contact with the touchscreen. In general, the term “touchscreen” refers to a physical interface for sensing electrical capacitances or capacitance differences within sub-areas of a defined area. In smartphones for example, touchscreens are capable of detecting the location of contact by a finger or stylus, together with acting as a display device.
Security documents capable of interaction with touchscreens comprise conductive elements applied on a non-conductive substrate.
It is an object of the present invention to overcome the drawbacks associated with security documents known from the prior art and to provide improved features which exhibit novel and surprising effects. An object of the invention is to make more difficult for the counterfeiter to replicate the conductive pattern.